A Lightswitch Guard / Stop to stop people from using the physical switch.

Fits common german wallswitchs, your mileage may vary.

The model is split up into a left and right part which may be printed individually, or as one for single-action switches.
Depending on whether it is a standalone switch or it has a socket or other switches above or beneath it, some parts of the sides may have to be cut away. 

Use double-sided (foam) tape for mounting.

Original onshape document can be found here: lightswitch guard